Scss compiler

It's annoying to have to deal with `.css` files directly when Foundation already uses [SASS](http://sass-lang.com/).

This pull request does a few things:

- It uses Jetty instead of Tomcat - this allows us to use the style sheets generated by SASS efficiently
- It includes JRuby so that we can run Ruby code in the JVM
- It includes the `sass` and `zurb-foundation` gems so that we can compile `.scss` files into `.css` files
- It changes the views to use the generated `.css` instead of pre-compiled `.css` files.